1. Field of the Invention
The present invention relates to a method for forming a semiconductor device. More particularly, the present invention relates to a method for forming a tungsten contact plug.
2. Description of the Related Art
Because semiconductor devices have become highly integrated and sizes of the semiconductor devices have been reduced, contact connections with higher aspect ratios may be used in a contact forming process. Void defects may occur in tungsten contact plugs even when the processes for formation of the contact are improved or optimized. This may be due to the present limits of semiconductor manufacturing equipment. As a result, it may be difficult to prevent the generation of void defects.
FIGS. 1 and 2 are sectional views illustrating a conventional method for forming a tungsten contact plug, and FIG. 3 is a plan view illustrating a planarized tungsten layer of FIG. 2.
Referring to FIGS. 1 through 3, a contact hole 40 for exposing a conductive region, may be formed on the semiconductor substrate 10 which may have an insulating layer 20. A titanium nitride (TiN) layer, which may be used as a barrier layer 30, may be formed on the resultant structure by a blanket method. A tungsten layer 60, which may function as a conductive layer, may be used to form a contact plug. A tungsten contact plug 60 may be formed by etching the tungsten layer 60 using chemical mechanical polishing (CMP) or an etchback process.
When filling the contact hole 40 using the tungsten layer 60, void defects 50 may occur in the tungsten layer 60 as shown in FIGS. 2 and 3. Void defects 50 may occur due to the different of deposition rates of the tungsten layer 60 inside the contact hole 40 and outside the contact hole 40 when depositing the tungsten layer 60 using chemical vapor deposition (CVD). More specifically, because the tungsten layer 60 may be deposited better outside the contact hole 40 than inside the contact hole 40, the inlet of the contact hole 40 may be clogged. As a result, a source gas, which may be used to deposit the tungsten layer 60 in the contact hole 40, may not be introduced inside the contact hole 40 and cause void defects 50 to occur.
The void defects 50 may deteriorate the electrical characteristic of a contact portion of semiconductor device. Therefore, the void defects 50 should be reduced and/or prevented in order to improve the characteristics of the semiconductor device.